Nearly 25 years ago, Senator John McCain observed that “a force begins to go hollow the moment it loses its overall mix of combat capabilities in any one critical area.” Last week, Air Force Chief of Staff David Goldfein quoted those words when questioned about the posture of today’s USAF.

No, General Goldfein didn’t say that the Air Force is now hollow. He did, however, flesh out McCain’s definition of what makes a hollow force: “When we talk about a hollow force holistically, we have to talk about all of those things that go into producing a ready force. And it’s training and it’s personnel and it’s equipment, and they all have to come together.”

The Heritage Foundation published an independent assessment of Air Force readiness earlier this year that touched on several of those markers. That analysis was based on the testimony of senior Air Force leaders, historical readiness levels, current threats, funding levels, and operational insights gleaned from surveys and interviews with 46 active-duty Air Force fighter pilots.

That assessment found that only four of 36 active-duty fighter squadrons are ready for conflict with a near peer competitor. It also found that fewer than half of active fighter squadrons could be deemed “ready” to prevail in even lower-threat wartime missions. That could mean as many as 17 squadrons are not ready to succeed in combat.

The Air Force has determined that it needs 3,643 fighter pilots. At the end of 2016, it was 873 short. That might not be so worrisome if all the pilots on hand were at the top of their game. Unfortunately, they are not. Cuts in funding have resulted in lower standards of both flight-school training and what constitutes a “mission ready” pilot.

From 1981 to 1990, the average graduation rate for candidates going through basic flight training was 75 percent. The highest single-year rate recorded over that time was 81 percent, logged in 1981. But after 1990, the rate exploded. From 1991 to 2015, the graduation rate averaged 91 percent; the lowest graduation rate was 1991’s 85 percent.

At the height of the Cold War, the NATO standard for fighter-pilot flying time was 200 hours per year. Fighter squadrons would not take pilots who flew fewer than 150 hours a year into combat, as they were far less likely to survive their first missions and their lack of competence would put other pilots and the mission itself at risk.

Today, the average U.S. fighter pilot receives 150 hours of flight time in training each year, and even that low average is inflated by units that deployed to Syria, Iraq, and Afghanistan, where threats in the air are rare, operational demands are low, and the ability to train for the real mission is non-existent.

As for the fleet itself, it is old. The average fighter has been in service for well over 25 years, which means it’s much harder to maintain. Unfortunately, the maintenance-staffing shortfall is approaching 4,000, as the most experienced artisans within that realm leave for private life. The impact has been predictable. The sortie rates for Air Force aircraft are now at historic lows — well below those the Air Force endured during its previous nadir, during the Carter administration.

When you take a hard look at the current status of training, personnel, and equipment, then, there is no question that the Air Force meets the definition of a hollow force.

All service chiefs can only be so transparent when speaking about the readiness of their forces. Each works directly for the secretary of defense, and while piping up during closed-door sessions will most always be encouraged, speaking negatively about readiness in a public forum is rarely permitted. Telling the world a service is “hollow” may expose its weaknesses to an enemy who might otherwise be unaware of them. It could also have a negative effect on recruiting efforts and the morale of those currently serving.

There certainly is a risk of exposing chinks in the armor to an enemy who may not be aware, and while it may make sense to some that people within the services “would know” how they are doing, the reality is somewhat different. The average soldier, sailor, Marine, or airman is not part of an operational unit and doesn’t have an innate grasp of combat readiness. While those in operational units should have a feel for their units’ readiness, they may not see the bigger picture unless a senior leader paints it for them.

Nevertheless, the facts are indisputable. We cannot continue to ignore our military’s deteriorating state of readiness in hopes that a rogue nation won’t take advantage of it. Congress needs to make this discourse a public one and move immediately to rescind the sequestration-budget caps that hamstring our ability to stop this downward spiral.

The level of funding required to completely reverse the current downward trajectory of our forces is significantly above even that proposed by Senator McCain earlier this year. But his proposal is a step in the right direction, and one this nation must take immediately.